Meaure inner diamter of tube <1in

[Horatio]

Hi all, I want to build a profile of the inside of a trombone. Really there are just a couple of pieces that I'm interested in but it would be interesting to try and get the whole thing. The inner diameter does vary somewhat along the lengths of tubes that make up the instrument but I'm at a loss for what tool to use to get this or if a machinist would be able to so this for me. I'm a little leery at taking it to an industrial machine shop but my bet is there are places that deal in this type of thing.

Most of the length is around .562 inches FYI.

Any ideas?

Thanks

Greg

 

[exranger06]

You need a measuring caliper. There are many different kinds. You can get them at an auto parts store.

 

[larryinnewyork]

Look on E-Bay for "Telescope Gauge"

You would need a 1" Micrometer or Caliper to then get a dimension.

 

[Trav]

You need an inside micrometer like this for tubes. This one is a Starret and expensive but you might be able to borrow one, ebay or get a cheaper brand.

 

[KD0AXS]

Originally Posted By: exranger06
You need a measuring caliper. There are many different kinds. You can get them at an auto parts store.


Yep.

#1 measures outside diameter
#2 measures inside diameter
#3 measures depth

Edit: Or what Trav posted there would work well too, especially if you need more precise measurements.

 

[NJC]

Unfortunately the pics are blocked at work, so I can't see what was posted. Here's Starrett's dial bore gage:

http://www.starrett.com/metrology/metrol...sortBy=none/asc

And search for "dial bore gage" too. They are expensive ... a decent machine shop might have - phone and ask how much to take a few measurements?

 

[NJC]

Horatio - another method is to use a micrometer to measure the trombone's wall thickness, then take careful caliper measurements and subract the wall thickness to find the ID (inner diameter).

 

[Horatio]

thanks for the great info all, I'll have a look at those.

One problem with calipers is that I'm going to be trying to measure a venturi that could be several inches inside the tube. Also, some of those instruments look like they might be a little large to fit inside the tubing of my trombone but I'll look at their specs more closely and see.

This definitely gives me better info on what I'm looking for so much appreciated. Hopefully I can rent or borrow some of it.

Cheers!

Greg

 

[Shannow]

In that sort of example, I use dental putty. It's non stick, no shrink, and designed to take accurate replications of complex surfaces.

 

[Horatio]

that's a great idea.

I'll dig around on the net to answer this myself but is that easy to come by? It's literally just the stuff my dentist uses?

 

[DBMaster]

This is the stuff. I remember the orthodontist making molds of my teeth with it. It is alginate, a seaweed product.

Amazon - Alginate

Just one example. You may want to see if you can find it cheaper elsewhere, but this tells you what to look for.

 

[Trav]

Try these and use either a electronic caliper or outside micrometer.

http://www.amazon.com/Anytime-Titanium-C...4589&sr=1-1

 

[NJC]

Originally Posted By: Trav
Try these and use either a electronic caliper or outside micrometer.

http://www.amazon.com/Anytime-Titanium-C...4589&sr=1-1

That's a good inexpensive option as well.